Dispensing devices such as metered dose inhalers (MDI) are well known. They typically include a tubular housing in which an aerosol container is located and an outlet tube leading out of the tubular housing. When used for dispensing medicament which is contained in the aerosol container, the housing is held by the patient in a more or less upright position and the outlet tube is placed in the mouth or in the nose of the patient. The aerosol container is depressed inside the housing to dispense a metered dose of medication from the container which is then inhaled by the patient. The actuation of the container is for instance recorded by an electronic counter in the device which stores the number of doses of medicament remaining or dispensed from the container. The dispensing device comprises an electronic display which is modified each time a metered dose is dispensed. The display provides an indication of the number of distributed metered doses or the number of metered doses remaining to be distributed.
An electronic counter and an associated electronic display of a drug delivery device, such as a dispenser, require a power supply to operate. The power supply is generally a battery mounted in the dispenser. There are however several problems associated with the use of a battery source in a dispenser. First, there is a risk that due to possible premature failure of the battery the electronic counter and the associated electronic display cannot work anymore. Second, it is bulky so that there is a need for space in a dispensing device to accommodate a battery. Third, a battery presents a risk of toxicity in the event of electrolyte leakage. In addition, environmental directives require a battery to be recovered when a used dispensing device is disposed of.
International patent application WO-A-2004/039443 concerns a fluid dispensing device which does not include any battery. The device comprises an electronic circuit which drives a dose indicator. The dose indicator includes a static non-volatile liquid crystal display (LCD) not requiring any energy for maintaining the display unchanged in a stationary mode and requiring very low energy to modify the display. An electromechanical generator, such as a piezoelectric actuator or an electromagnetic coil, provides the low energy required to energize the electronic circuit and to modify the display during actuation of the dispenser.
A disadvantage of static non-volatile LCD displays is that they are expensive compared to standard LCD displays. The term “standard LCD display”, as used in this document, refers to a display which requires power to be readable. A further disadvantage is that an insufficient amount of power may be generated during actuation of the dispenser to modify the displayed value on the static non-volatile LCD display
It would thus be desirable to provide a dispensing device including a relatively cheap LCD display which is operable by a battery-less arrangement.